1. Field of the Invention
The field of the invention relates to data processing and in particular to fault diagnosis on virtual machines.
2. Description of the Prior Art
It is known to provide debugging facilities for virtual machines. For example, a standard KDWP protocol has been developed to debug java applications on a virtual machine. The KDWP protocol has been adapted from the JDWP protocol to provide diagnostic operations on virtual machines with low memory resources. The KDWP protocol provides a subset of the JDWP functions and is adapted to process operations with high memory constraints on the host rather than on the machine being diagnosed.
FIG. 1 schematically shows a java debugger according to the prior art. Java debugger 10 is typically located on a host computer such as a PC and sends known java debug chains to the java enabled device 20, which in this case comprises a debug proxy 22 and a java virtual machine 24. The java proxy 22 receives the java debug chains in the JDWP protocol and converts them to KDWP protocol and then sends the appropriate diagnostic signals to the java virtual machine 24 which may comprise breakpoints, stop/starting diagnostic signals for the virtual machine or data to be processed by the machine. Diagnostic data is then captured by the debug proxy 22 and sent back to host debugger 10.
Java virtual machines are now able to run multiple applications in parallel. Such machines are not able to be debugged using known techniques such as that illustrated in FIG. 1 as the debug proxy 22 cannot tell which application a particular thread on the virtual machine belongs to.
It would be desirable to be able to debug virtual machines running multiple applications using pre-existing Java debug chains that have already been developed and whose properties are known. The ability to use pre-existing java debug tools would enable programmers to use tools they already know and also allow them to choose a tool with appropriate features from the wide range of already developed tools.